1. Field of the Invention
The present invention relates to offset duplicator machines. In particular, the present invention is directed to apparatus for attachment to cylinders of an offset duplicator machine to adapt the machine for uses other than offset duplication, such as serial numbering, general printing, scoring and perforation of the stock. Specifically, the present invention is directed to apparatus to be attached to the blanket cylinder of an offset duplicator machine which is designed to accommodate a serial numbering device, a signature logo or design block, a scoring implement, or a perforation implement, so as to convert a standard offset duplicator machine into a multi-purpose apparatus.
2. Discussion of Background and Material Information
A standard piece of equipment in most modern print shops is an offset duplicator machine. This type of machine has been found to be particularly suitable for duplication or printing of most types of business and office stationery including business forms, such as invoices, as well as advertising and promotional materials. Although many jobs for which offset duplicator machines are used do not require additional functions, many require that the stock be either perforated or, scored or be provided with serial numbers or other printed matter, such as signature, designs, logos and the like.
Commercial products are sold for the purpose of adapting a standard duplicator machine to have additional capabilities of scoring and perforation. U.S. Pat. Nos. 2,842,202 and 3,554,070 relate to such attachments. A common brand of such attachments are "Litho-Slit" and "Litho-Perf" which are metal strips to be applied to the impression cylinder of a duplicator which, when compressed against stock passing between the blanket cylinder and the impression cylinder, causes the stock to become scored or perforated, respectively, as the case may be. A common problem associated with such attachments, however, is that they impart localized pressure against the blanket at the score and perforation site which ultimately damages the blanket. Another disadvantage is that such adhesive strips are not amenable to adjustment once they have been placed on the cylinder.
Although efforts have been made to modify conventional printing presses to accommodate a serial numbering printing unit, such attempts have not met with much commercial acceptance or success. Typically, in serial number printing units, the serial number is printed by the numbering device on the surface of a sheet of stock which will face a blanket on the periphery of the impression cylinder when the sheet passes between the cylinders. Thus, the printed serial number tends to be transferred from the sheet onto the blanket under pressure imposed when a pattern is imprinted on the sheet. The transferred serial number is then transferred from the blanket back onto a next sheet where it bears a newly printed serial number. Attempts have been made to eliminate this problem by cutting a hole in the blanket at a position aligned with printed serial numbers to avoid the build-up of ink on the blanket which can blur the transfer of the image. Such a modified blanket, however, is destroyed for purposes of printing. Moreover, this unit does not have the capabilities of scoring and perforating nor is designed to accept signature and/or design blocks. Thus, it is not a multi purpose unit.
In addition, apparatus for printing serial numbers on sheets of stock material, such as that which is disclosed in U.S. Pat. No. 4,481,878, have been developed in an attempt to improve earlier number devices Such serial numbering machines typically imprint the serial number simultaneously with the other impressions. Although such an apparatus is advantageous in that it permits one-step printing and numbering, as a practical matter, it poses problems which have been difficult to overcome. In this regard, the most common problem associated with a one-step printing and numbering apparatus is that the sheets of stock material are numbered in series without any regard for the quality of the printed material on the stock. Normally in the course of printing operations, a certain number of the sheets of printed material are unacceptable for one reason or the other. A common defect would be smudged lines or nonuniformity of the printed image. For a typical run, this poses no particular problems in that it is a simple matter to dispose of the defective sheets. In a run, however, where the sheets are provided with serial numbers, the solution is not so simple. If the reject sheets are observed soon enough, the machine can be stopped and the serial numbering device reset to begin the numbering of the sheets as of the number of the reject sheet. If, however, reject sheets are not discovered until the run is completed, special measures must be taken to provide replacement printed sheets with the appropriate numbers. This is a particularly time-consuming and, consequently, expensive procedure.
Representative examples of offset printing machines equipped with a numbering device include U.S. Pat. No. 3,611,921, wherein a plurality of numbering mechanisms are mounted on a sprocket wheel shaft of an endless chain delivery which cooperates with a counter pressure roller which is located downstream of the impression cylinder of the offset printing machine in the travel direction of the sheet being fed therethrough. This is in contrast to prior conventional printing machines wherein the numbering devices may be located directly at the impression cylinder of the offset printing machine. The numbering mechanisms are located on a circular segment around a sprocket wheel shaft in the region of the periphery which carries the imprinted surface of the sheet when the sheet is being moved from the counter pressure cylinder.
U.S. Pat. No. 3,728,960 is directed to a number-printing apparatus which is mounted to an otherwise conventional offset lithographic printing apparatus, including a conventional main cylinder having a plate segment and an impression segment which revolve with the main cylinder in contact with the smaller, lower cylinder that is normally covered with a thick rubber surface mat or blanket. The number-printing apparatus is capable of end-wise withdrawal from the printing zone for convenient, rapid resetting of the numbering mechanism, when this becomes necessary.
U.S. Pat. No. 1,931,566 is directed to a rotary machine used for numbering sheets of paper stock which includes a plurality of rotatably mounted numbering head-wheels which have a coacting impression roller which are rotatably innerconnected.
Notwithstanding the prior art attempts to provide a convenient serial-numbering device for use with offset duplicators and other printing apparatus, it is not believed that prior art attempts to resolve the previously discussed problems have done so in a manner which is as simple and yet as effective as accomplished by the apparatus of the present invention, as described in more detail hereinbelow. More particularly, prior to the present invention, it is not believed that cylinders of conventional offset duplicator machines had been adapted to receive a serial numbering device, a signature logo or design block, a scoring implement or a perforation implement so as to convert a standard offset duplicator into a multi purpose apparatus.